The legacy of the Cleveland Elementary School shootings is evident 20 years later. Change is a big part of that legacy.

The shootings had a major effect on the gun-control debate in the United States. They brought into focus the issue of school safety like no other campus shooting had to that point.

The attack stands as a stark warning of the vitally important need to identify and help mentally disturbed people before they commit an atrocity. And it was one of the events that raised awareness of the stress reactions people often suffer years after experiencing a tragedy.

A look at things that changed in the wake of the Cleveland shootings:

The mere utterance of Columbine High School (1999) or Virginia Tech (2007) resonates vividly for most people when asked to recall deadly campus sieges.

Those and other shootings have stirred the national debate over gun control.

Yet advocates on both sides of the issue agree that the attack 20 years ago on Stockton's Cleveland Elementary School was a flashpoint in the movement to ban assault weapons.

"The Stockton schoolyard shooting was so horrific it spurred people into action," said Brian Malte, director of state legislation for the Brady Campaign to Prevent Gun Violence. "California blazed the trail."

Within weeks of the attack, leaders in Stockton adopted an ordinance banning semiautomatic assault weapons. By year's end, California's lawmakers had followed the city's lead with what would become the strictest ban in the nation.

There is no federal law banning assault weapons.

A 1994 law - the federal Assault Weapons Ban - expired in 2004 as part of the legislation's sunset provision. It included provisions prohibiting the sale to civilians of certain semiautomatic rifles. Malte said he believes President-elect Barack Obama will take up the issue again.

Sam Paredes, executive director of Gun Owners of California, opposes the ban on assault weapons, agreeing that Patrick Purdy's spree at Cleveland created an "emotional furor" that swept the nation.

"It takes one crazy person to start a fad," Paredes said. "The reaction caused even pro-gun politicians to get weak in the knees and go along with it."

Purdy could have committed the atrocity with almost any firearm, Paredes said.

Retired Stockton Fire Chief Gary Gillis had been one of those who believed people had a right to keep and bear arms. The Cleveland shooting altered his views.

"I've seen what they do," he said. "I clearly know he could not have been so destructive if he just had a hunting rifle."

Stockton Unified School District Police Chief Jim West says the Cleveland Elementary School shootings present a particularly troubling scenario for those charged with limiting the scope of such tragedies or trying to prevent them.

"The Cleveland School shooting is one of the real nightmares," West said. "You have someone who has no connection to the school, so there's no warning, ... no way for anyone involved with the school or the police to have any inkling that this guy was going to show up and start shooting."

In fact, the 24-year-old Purdy had attended Cleveland, but by 1989, it had been nearly 16 years since he had been a student there.

West and other security professionals say they believe schools are better prepared to quell an attack today than 20 years ago, whether the attack comes from within or from without.

School personnel, West said, are more vigilant than they were 20 years ago because of the numerous school shootings the past two decades. New measures add to security:

» People who enter campuses are required to check in and wear identification badges.

» Lockers have been removed, eliminating a place where weapons might be stored.

Still, security officials worry.

"Where may the violence come from?" said Kenneth Trump, president of National School Safety and Security Services. "The answer, in short, is anywhere."

Dan Castillo, who volunteered as a first responder at the Cleveland shootings, said school safety was a big reason he ran for a seat on the Stockton Unified school board in 2006. He's now in his second year as school board president, and school safety remains a policy priority.

Retired Cleveland Principal Pat Busher believes that schools "failed" Purdy by not adequately intervening when he was a troubled little boy.

Twenty years after the Cleveland shootings, Busher remains concerned that schools aren't doing enough to help troubled children at an early age.

"We've got to do better with our interventions and our mental health to help children work through the problems of childhood so they don't grow up to be angry adults and monsters who hurt other people," Busher said in an interview with former Record reporter Dianne Barth.

"I see more and more angry children in our school systems every day, and we've got to respond to their needs and work with them so that they can have positive and productive lives."

John New, who heads Stockton Unified's student assistance program, said the district relies heavily on teachers and other staff members to identify troubled students and refer them to school counselors.

Retired Cleveland teacher Mary Stirton still works as an elementary school substitute on occasion. She is concerned by what she sees.

"When you see them struggling now, ... just dealing with their parents having a hard time for various reasons, lots of times they seem to be the head of the family, and they're not very old," Stirton said. "I don't know how we can do it, but I think they need to have help with what they're dealing with. We have to realize they have a lot of problems before they get to school."

Marianne Castillo was working as an instructional assistant at Walton Special Center on the day of the Columbine High School shootings nearly 10 years ago.

Columbine hit her hard. It had been 10 years since she'd helped wounded and terrified children at Cleveland Elementary School, where she was working in 1989. A decade later, she hurried to Cleveland on the day of Columbine and sought out Busher.

"Pat," Castillo said, "I need help."

Busher, a psychologist by training, talked Castillo through her feelings.

Castillo and many others who were at Cleveland 20 years ago continue to feel the effects of what they experienced.

"With Iraq and Vietnam and the post-traumatic stress syndrome, I think people are more accepting and understanding that it is real," retired Stockton Deputy Police Chief Lucian Neely said. "I had a very difficult time, but I've blocked a lot of that out. I don't really remember a lot of it."

Many continue to struggle. An unexpected loud noise or even being on a thrill ride at an amusement park can trigger a stress reaction.

Cleveland Assistant Principal Lori Risso was a new teacher at the school 21/2 years after the shootings. At an orientation on her first day, she sat in a room with teachers. Nearby, a contractor began to use an air-nail gun.

"One of the kindergarten teachers at the time heard the nail gun go off," Risso said. "It was kind of loud. She dropped to the floor, and the teacher in the workroom started crying, and then teachers came from everywhere to comfort her and knelt beside her."

Former Stockton Fire Department public information officer Marty Galindo said he can still smell the helicopter fuel and antiseptic when he thinks about that day.

Marianne Castillo said lingering feelings of uneasiness and danger creep into her thoughts even when she is engaged in a favorite activity, such as riding a roller coaster at Disneyland.

"I'm ... very terrified, because I know the unthinkable can happen," she said. "I wasn't surprised when the World Trade Center blew up. I wasn't surprised. Do you know why? Because those things that aren't supposed to happen, I know they happen. I know they happen."